1. Field of the Invention
The present invention relates to module connecting systems in which expansion modules are connected to basic modules.
2. Description of the Related Art
In various module connecting systems such as sensor input devices to which external storage devices can be added in module units, lines such as power supply lines, input/output signal lines and data bus lines are disposed in a backboard of each module, various circuits such as a package having a sensor input function are mounted on a slot of each module, and all the modules can be connected to one another through wiring of the backboard (for example, see Japanese Patent Application Laid-open No. 5-307426). In such systems, as illustrated in FIG. 1, there is proposed a method for confirming the presence or absence of an expansion module by communication with a microcomputer incorporated in the expansion module. As illustrated in FIG. 2, there is also proposed a method for determining the presence or absence of the expansion module by a contact connected to each expansion module.